could you help me please in Parallel and GPU Computing?

I am implemented a Parallel and GPU Computing in neural netwrk by used this instruction below

matlabpool open
net2 = train(net1,x,t,'useParallel','yes','showResources','yes')
y = net2(x,'useParallel','yes','showResources','yes')

and also

net2 = train(net1,x,t,'useGPU','yes')
y = net2(x,'useGPU','yes')

and I have a good accelation but I dont understsnd how it is work, and any type execution by this statmente, data parallelizaion or node parallilization